determining array lengths

[Brad Allen]

>  > After looking around in the documentation, I haven't
>>  been able to find a simple function to determine the
>>  number of keys for a given array dimension. Do I need
>>  to parse the output of the keys function for this, or
>>  have I overlooked something in the documentation?
>
>See the extents function.

Aha. Thank you. I had misunderstood the wording of this function in 
the Transcript dictionary. The part that threw me off was this part 
of the at the end of the entry under Extents:

"Each line contains two numbers separated by commas. The first item 
is the smallest number of an element in that dimension, and the 
second item is the largest number."

Is this misleading, or am I just misunderstanding this text? My 
reading of this is that Extents provides the lowest and highest 
values in the Elements of an array (sort of like the min and max 
functions), not the index keys. But in reality, as I'm glad to learn, 
the Extents function provides the lowest and highest values of the 
index keys in an array dimension.